EP0677234B1 - Method of polarizing acoustic fields in particular with the aim of achieving an extremely broad, non-localized and spatial stereo effect requiring little space - Google Patents

Abstract

A process is disclosed for producing polarized acoustic fields. The directionality thereby obtained in a very wide auditory range, even with a very small monolithic, purely passive system, results in a subjectively unusually broad spatial stereo effect. The ability of bodies (acoustic "conductors", including "insulators" or action reflectors for mirror sources) to create at least one spatial preferred direction for the wave progression by means of internal structuring, special geometries and surfaces is exploited to this end (polarization). Longitudinally structured bodies, especially clusters of capillary tubes, have this ability and favour one longitudinal component of the acoustic progression. The record-side acoustic 3-D space appears to be reproducible in phase using acoustic transducers according to the process to a large extent without electronic aids. However, active smoothing of frequency-response and phase-response advantageously compensate for certain system-related features. Electronic delay units simulate the behaviour of the enclosure of a system according to the invention and improve its characteristics.

Description

The invention relates to methods for reproducing acoustic wave energy according to independent claims 1, 2, a device for carrying out these methods according to claims 3 to 5 and a method for absorbing acoustic wave energy according to claims 27 and 28 and devices for recording according to claims 29 and 30.

Furthermore, the invention relates to arrangements from the devices according to claims 35 to 38.

Developments of the methods and devices are the subject of the dependent claims relating to these claims.

General process description

The method according to the invention effects the polarization of acoustic wave fields. The excitation of a progressively running wave front (eg impulse) acts along defined lines in the longitudinal direction of the excitation system, with the velocity vectors of the ideally orthogonal, co-planar wave surfaces, so-called "plane waves". A polarizing dipole per axis is created via lateral poles and system-specific transit times.

1. State of the art

• 1.1. Hearing-adaptive acoustics
  • a) On the recording side of artificial head stereophony, the Dymmy Head, representative of any number of listeners, is positioned in the concert hall and the signal, usually via headphones, is ported to the listeners.
  • b) Headphones provide directional acoustics at approximately 180 degrees (right-left, quasi-axial) and thus a realistic stereo impression. The axis of the playback system is parallel to the auditory axis (adaptive to hearing). The main disadvantage is that headphones only reach one person per system.
• 1.2. Usual speaker arrangements, the stereo triangle, problems
  • a) Since a loudspeaker (playback converter) cannot radiate efficiently due to the so-called acoustic short circuit (deletion of the sound pressure on the front through the rear and vice versa), it is mounted in a closed housing or on a baffle. Reactive forces (actio = reactio) are released onto the walls. The walls vibrate all around and reflect sound waves. Housing resonances have a sound-enhancing effect, especially in the bass range (bass reflex). This is used to smooth the frequency response of the converter. The reflected waves, housing shape and material influence the fidelity.
  • b) Usually two speakers are arranged so that they form completely independent, separate wave fields. The intensity of the waves emitted by each (theoretically approximately punctiform) acoustic transducer decreases with the square of the distance. Hence the conveying of a stereo impression So far, this has been a problem for several listeners with loudspeakers (also using electronic aids). A deviation of just a few cm from the center line shifts the stereo image considerably. Most of the time, multi-path systems no longer have the same phase due to the different runtimes.
  • c) Outside the center line, the stereo effect decreases significantly, since both the running time and the intensity (with the square of the distance) are falsified. Usual stereo arrangements therefore only give a good stereo impression on the center line between two loudspeakers. Positioning in an equilateral triangle is preferred. The differences in intensity thus allow the virtual sound sources to be located well. This "bondage" is annoying. Monolithic systems are desired that give a stereo impression regardless of position.
• 1.3. Known monolithic stereo speaker arrangements
  Speaker arrangements in a monolithic design are known. However, they contain relevant reflected sound components of the boxes with the help of the side walls.
  • a) Loudspeakers were already installed on the side of radio equipment before the market launch of stereophonic systems. A so-called "3D circuit" creates a spatial impression, for example by reversing the polarity of a converter.
  • b) In 1959 LEVI, Sidney, et al. in THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, Vol. 31, No.9, (Listener Reaction to Stereophonic Reproduction by Reflected Sound, pp. 1256-1259) that listeners find a monolithic stereo system with loudspeakers radiating in opposite directions as very spatially and overall better assessed than separate boxes. To reinforce the effect, axially parallel panels, in particular side, reverberant wall reflections, were used.
  • c) Monolithic stereo systems such as simple baffles, the so-called stereolite according to US-PS 4,837,826 or FR-PS 2,345,046, the internally separated "flexible tube" according to US-PS 4,501,934, the tubular body with two sound transducers according to US-PS 3,995,124 already exist, but in principle work with considerable reflections on assembly or partition walls. As a result, reflections and turbulence occur on the exit side, which significantly worsens the stereo effect.
  • d) It is also known from EP 0 256 688 A2 the arrangement of loudspeaker and microphone pairs in a tubular body. Here, the speaker or microphone pairs are inclined extremely obliquely to the main direction of the line of action, which leads to a significant deterioration in the stereo effect. In addition, microphones and loudspeakers are disadvantageously encapsulated against one another.
  • e) Finally, from US Pat. No. 5,109,416 a loudspeaker arrangement for stereophonic reproduction of sound waves is known, in which two loudspeakers are arranged in a conventional manner on the central partition wall of a housing in an antiparallel manner. The arrangement is such that turbulence forms inside the housing, which counteracts the stereo effect.

2. Task

The invention has for its object to provide a method and devices and arrangements which enable stereo reproductions with small dimensions of the playback arrangement with good spatial resolution practically in the entire playback room. In addition, an optimized recording arrangement is to be created for this.

3. Known elements for the solution

• 3.1. Known basics
  • a) As is known, corners and edges form "singularities" for fields, that is to say disturbances. As is known, any type of falsification of a radiated acoustic waveform can make itself felt in the sound image (harmonics). Sound waves "flow" through the airspace at a speed of about c = 340m / sec. Therefore, additional inertia problems are to be expected at corners or edges for such particle waves.
  • b) Waves consist of progressive (= continuous) and reflected regressive (= returning) waves. The respective portion with the same intensity (amplitude) becomes the "standing wave". Multiple reflections in one axis (back and forth) provide a "resonance", as well as waves rotating on a circumference. In Fig. 2a, the direction of progression of the shaft is denoted by P.
  • c) On the recording side, the disturbance in the room can already be minimized by extremely small recording converters.
    The punctiform microphone capsule, which hardly influences the sound field and whose dimensions are small in relation to the transmitted wavelengths, has already been implemented. It then neither causes reflections that distort the field image, nor diffractions, and does not result in a physical separation between the right and left channels, provided that large housings and separators are not used. Nevertheless, microphones with small diaphragm diameters and spherical characteristics above 1 kHz often have increasing directivity.
    The directional tube microphone is known. It takes advantage of the fact that the sound waves can be collected through a pipe by aligning themselves along its longitudinal axis. Cylindrical bodies, solid or tubular, therefore generally promote wave propagation along their axis, the linear coordinate of a cylinder coordinate system.
  • d) The ideal of a "spotlight" is missing on the playback side. As is known, the sound pressure of a system that is only approximately point-shaped in comparison to the minimum wavelength is not sufficient. Acousticians require a spherical propagation of the wave from the playback source. As illustrated in Fig.1a, the associated eigen-functions in the propagation space are wave equations in the sphere coordinate system.
    For sound waves, loudspeakers form an extreme disturbance in the room because they have a size that is a multiple of the size of the recording transducers. For the same reason, their directional effect is clearly pronounced. The built-in housings, baffles and the like are even larger. Although they prevent the acoustic short circuit and lead to an improvement in the frequency response, all walls are always reflective arrangements (e.g. bass reflex box) and their usual corners and edges disrupt (kink, for example) the sound flow. The wave equations of rectangular boxes are usefully described in the Cartesian coordinate system (eigenfunctions).
    Ideally, the sound flow should pass from one (internal, e.g. Cartesian room) to the other (external, spherical) coordinate system with as little interference as possible (low reflection and diffraction). A usual box prevents this with the geometry (corners, edges, side and rear wall). Thus, an object of the invention to achieve the object mentioned under 2 is a less disturbed transition of the sound flow (energy flow) of the progressively running sound wave in the reproduction room.
• 3.2. Approaches
  • a) The field image of a concentrically propagating (impulse) wave in the spherical coordinate system forms two spherical shells at two successive times. The tangential components on each spherical shell rise on. Therefore only radial components exist. Any conical segment (in the form of a funnel) between two spherical shells merges into a tube (cylinder coordinate system) with a very large radius. The end faces can be implemented as flat membranes with almost no field interference, which oscillate in the same direction (in the same direction) with a delay. Waves running along a cylinder coordinate system form so-called "plane progressive waves", as shown in Figures 1a and 1b in spherical and cylindrical coordinates.
  • b) The transitions from one to the other coordinate system are therefore fluid. If they are ideally reflection-free, the system is completed with its wave resistance according to the wave theory. Cylinder coordinate systems no longer need point emitters. Acoustic spotlights in tubes stimulate flat (coplanar, especially cylindrical) eigenfunctions. Acoustic wave emitters with a flat membrane are specially positioned to excite coplanar waves. Waves circulating in the pipe circumference (pipe reverberation, circumferential resonance) can be suppressed, for example, by a structure laminated in the circumference, in particular with damping (even partially air-permeable) intermediate layers. Especially longitudinally bundled fiber (rod) or tube structures inside (permeable, differentiated) avoid the formation of resonances, as indicated by the schematic representations according to Fig. 1b, 1c and 2b to 2f.
  • c) As is known, each curve can be viewed as an infinitesimal sequence of time-shifted superpositioned rectangular pulses (+/-). In principle, it is therefore sufficient to consider the effect of a single impulse. If an energy pulse at the beginning of a (thin) tube causes the deflection of a membrane, the wave runs inside and outside the tube at the speed of air and sound. The primary membrane impulse pumps a progressive wave forward. A terminal second membrane would move in the same direction with a time delay. The energy (wave) that arrives at the other end of the pipe after its running time flows further through the air movement (or second membrane) movement of the pipe diameter in space. Interferences (reflections, diffractions) are minimal in the direction of propagation. The parts audible in the rearward direction are known to be low. These relationships can be sensibly realized for the two independent parts of a stereo signal (see Fig. 1a: radial deflection)
  • d) Each membrane deflection caused by a force (actio) also causes a direct longitudinal reaction (actio = reactio) of the tube and an (almost) undelayed reaction of an opposite membrane, corresponding to the comparatively very high impulse or sound velocity in fixed Matter.
  • e) It is more difficult to understand the relationships in the frequency domain. Group delay times and strong damping of high frequency components occur, which falsify the pulse curve after a certain delay time or length. However, these errors can be compensated for by active circuits (for example by frequency compensation and delay elements), which emulate the relationship of the system to the outside.
  • f) The spatiality of a sound event has a particularly intensive and lasting effect on listeners. The overwhelming spatiality of recordings using interfacial microphones is known. The invention is based on the fact that something comparable is made possible on the reproduction side, for example by the directional progressive wave emitted by the above-mentioned cylindrical arrangement (tube) generating a progressively running surface wave by positioning it along a wall.
• 3.3 Result solution
  The facts explained above are used according to the invention selectively or in combination for the reproduction-side reproduction of sound waves in order to achieve a spatial stereo effect with minimal means.
  The reproduction methods proposed by the invention are the subject of claims 1 and 2.
  Devices for performing these methods and details of these devices are the subject of claims 3 to 18.
  Arrangements for reproduction composed of several devices according to the invention are the subject of claims 19 to 22.
  The following findings and properties are decisive for the generation of the spatial stereo effect.
  • a) If transducers are placed in two pipes, two independent signals run through their respective pipes. According to the superposition principle, this also applies to only one excitation at two points in one tube. Even this simple arrangement creates an astonishing spatiality along a surface (wall), especially when the stereo signal is emitted in the same direction (opposite pole = polarity reversal of a channel) and suppression of the pipe resonance (pipe reverb). The effect can even be verified in adjoining rooms, where conventional stereo systems no longer have any effect.
  • b) The entire behavior of the system towards the outside resembles a (thick) vibrating rod or body with oscillating end faces. Each frequency component can choose its share between the end faces of the system and close in phase in the exterior. On Solids, especially a pipe, with the desired properties can have a round, oval or square cross-section. Approximate solutions also arise from other elongated, rotationally symmetrical shapes (e.g. cones, ellipsoids as in Fig. 5 or hyperboloids).
  • c) The initially, primary, elementary spherical progressive sound waves are transformed into a coordinate system (own function), which is predetermined by the housing structure, including its openings. An elongated shape with low-reflection and end openings deforms the spherical shape of the progression in the longitudinal direction. Even with relatively large deviations from the ideal forms and non-ideal structure, the effect is still clearly audible, since the hearing is an extremely sensitive organ of perception.
  • d) Secondary effects, especially reflections and resonances, are not initially desired, but are permitted. Such disturbances are secondary and do not correspond to the method according to the invention, since the principle should primarily only produce progressive waves, that is to say continuous portions of waves. However, less ideal implementations are still within the scope of the invention. Reflected energies and resonances must not, at least in the location-relevant midrange and treble range, disturb or even destroy the effect, especially the stereo base, which is widely widened regardless of location. In particular, resonances in the bass range that are not location-relevant may be permitted.
  • e) A casing of the above-mentioned shapes may form differently shaped housings, because covering or positioning behind, on or under bodies shows improvements. The existence of directed, for example equidistant, basic structures is important. This includes simple tube structures, including a bundle of thin tubes inside, as stated in claim 8.
• 3.4 Terminology and explanation of the effects achievable with the invention
  • a) A parameter that is identical in every spatial direction is called SCALAR and is conceivable as a concentric (elementary) sphere with a homogeneous property everywhere. Crystals, for example, do not meet this requirement.
    A parameter that is only judged in one dimension (structure, spread) describes a VECTOR.
    Three (orthogonal eigen-) vectors, i.e. different parameters in each direction, form a TENSOR.
    If all vectors of a tensor are identical, this tensor tapers again to the scalar. A scalar concentric field, just like such a wave, is purely spherical, both elementary and macroscopic.
  • b) In the known ACOUSTIC SHORT CIRCUIT, the pressure wave generated on the front of a loudspeaker diaphragm (largely) deletes the tension wave generated on its rear (negative pressure wave). This leads to, for example, superposition of pressure and tension in the hearing to quasi-simultaneous deletion of a sound pressure generated on the front through the rear. Every dipole without a sufficiently long line of action results in a "zero" effect everywhere. - Runtimes prevent this. However, if they are created by partitions or panes, they distort the waveform through reflections and diffractions. The acute-angled edge of the wall forms an essential singularity. Since any distance that corresponds to a running time pulls the acoustic short circuit apart, the dividing wall can also be shaped as a funnel or tube, for example.
  • c) POLARISATION means: Not elementary concentric (spherical). This property of matter or waves A preferred direction, especially along a route with terminal poles, is polarized .
    • The preferred direction of a progressively advancing, plane wave is a directed finite line (vector). This can consist of one or more run-time-defined sections with terminal poles in the form of final interfaces (at least at the start of the tube made of membranes) of a really finite (cylindrical) system.
    • If the same, opposite sources coincide (distance = 0, ie short circuit of the poles), they result in 0. Only a finite line of action (sufficiently large distance) allows the existence of a kind of dipole moment.
    • The tube length (L) generates such a DIPOL MOMENT as a polarization path of an acoustically polarized dipole.
    • Polarization, as the main, unique directional property of a traveling wave, is primarily polarized , in contrast to properties acquired secondarily, such as a secondary reflection of the wave.
    • Similar to the electric dipole field, such fields have a right-left character throughout the room. The avoidance of energy storage (capacity, resonance) suppresses reflections. The vector P is shown in Fig. 2a.
  • d) If a tubular ring is selected, an emitted pulse runs around the ring as a pressure and tension wave on both sides. When the pipe is no longer closed, the impulse propagates in the outside air at the end of the pipe. If the energy runs in the opposite direction to the energy in the interior (reactive), a wave reaches the other side of the membrane with a delay. This appearance is analogous to the polarized magnetic field that closes over the environment.
  • e) An impulse stimulated in or on the straight tube (= group of frequencies) propagates on straight lines to the end of the tube (pole, section) without acoustic short circuit due to the wave propagation time. The wavefront forms surfaces (complementary to the progression line) that are parallel-even, i.e. co-planar, inside straight tubes.
  • f) Acoustically polarized such progressive sound waves are called.
    Hearing adaptive ( ear- correct) polarized is a wave direction that is adapted to the hearing or is easily adaptable. In particular, the vertical reproduction of a real horizontal sound event is not adaptive to hearing. It depends on the adaptive usability of the system with regard to location-relevant frequencies. In the case of a device for bass reproduction, for example according to EP 0 263 748 A1 and in a vertical arrangement, the effect according to the invention cannot be shown.
  • g) Two such tubes, each with a terminal converter, form a stereo arrangement . If instead two transducers in a tube are controlled independently of one another, i.e. with a stereo signal , the system delivers such a polarized and, from each transducer, quasi reflection-free progressive stereo field . With two transducers positioned on the side, for example, a straight tube can be aligned in the direction of hearing, i.e. adaptive to hearing, as a low-diffraction and low-reflection path. The distance between the transducers defines the signal transit time T and causes a kind of dipole moment similar to the mechanical pair of forces as levers or the dipoles in electrical engineering.
  • h) The room is subjectively enlarged. Even simple stereo arrangements reproduce the effect. The overall system can generate multiple phase rotations. Real transducers, as spring-mass systems, do not work without reaction and, at the end of the system mentioned, cause a damped "soft" reflection with their reaction. The returning part of the wave can run back and forth several times between the poles of the dipole and thereby act like the Hall parts existing in the original signal. In addition, pipes that are not damped by resonance can produce further, mostly undesirable, Hall components. The sound of overly simple embodiments is hardly acceptable due to the shortcomings. This must be compensated for, passively or actively.

4. Exemplary embodiments: simplest monolithic patterns

• a) A first exemplary embodiment is shown schematically in FIG. 2a. With this an acoustic parallel field is generated by an acoustically polarized stereo dipole. In its simplest form, an uninterrupted longitudinal connection is formed by a cylindrical body, namely by a cylindrical metal or plastic tube AC (acoustic conductor).
  A pair of transducers W1 and W2 are arranged coaxially with these. The easiest way to stimulate co-planar waveforms is through terminal, parallel, flat "pumping" surfaces, which act as sound transducers and act on the end surfaces of this polarizer or inside. As coplanar / poliplanar membranes serve as pumping surfaces.
• b) The damping of pipe resonances (pipe reverb) can advantageously serve, for example, laminated structures on the circumference or inside, for example by layered rod (pointed), fiber or bundle of tubes, as shown with the cross sections according to Fig. 2b, 2c, 2d and 2g is. Rolled-up corrugated cardboard (eg narrow inside, wide outside) according to the cross-section in Fig. 2e and 2f is also an advantage. Control of the converters in the same direction (opposite polarity) leads to a wide spatial effect. Bipolar (also artificial head images) are well suited for the demonstration of this effect.
• c) The polarity reversal of a converter (artificial similarity) leads to a surprising spatiality of the reproduction. Wall reflections are not required. Because of the recording technology, which has so far been completely uncorrelated with the playback process, this effect with conventional polarity only becomes clear with slightly better stereo recordings.
• d) In a simple embodiment, a pair of conical full-range loudspeakers with a diameter of 10 cm are glued into a hard, about 1 meter long, plastic tube dampened with cotton and 2 mm wall thickness. Partitions are avoided because they promote reflection, pressure build-up and cross components. With such an arrangement, the effect is already clearly perceptible.
• e) With greatly reduced bass reproduction, this effect can be achieved with short, thin metal tubes with a length of approx. 33 cm. To produce these metal pipes, 0.25 mm thick, hard-rolled aluminum sheet can be rolled up into a cylinder with a diameter of 4.5 cm and more, the interior being filled with cotton wool for damping. Terminal, "pumping" broadband loudspeakers in the same direction (opposite poles) already provide a wide, spatial stereo effect.
• f) With larger diameters, the tube is rolled from three overlapping parts with intermediate layers. The effect can be improved by using inner connecting channels, for example in the form of a bundle of round rods, fibers, tubes of different lengths. Co-planar loudspeaker membranes improve the height reproduction (phase).
• g) A good spatial effect can be achieved if the device designed according to the invention is parallel to the wall, e.g. behind the approximately centrally positioned television set. Here there is a lateral radiation, whereby the side walls of the room should reflect only moderately. For example, there is an improvement side damping, e.g. through needle felt or curtains. Further improvements result when the device is positioned on a long shelf. The effect is clearly audible even outdoors, i.e. without side reflection, lying on the floor and / or in front of a wall.

5. The sound effect achieved

• a) With playback devices or arrangements according to the invention, a stereo effect which is distributed throughout the room and is distinctly spatial and clear is achieved. In a playback room, the system creates phase effects that simulate a very broad subjective location of the virtual sound sources (musical instruments, voices) right down to the side walls. The axial preferred direction of the running waves is reinforced by room walls and ceilings or supports (shelf surfaces) lying behind the playback device, which can be explained by the bundling effects of the system reflected on the walls. The amplification of the spatial effect by walls parallel to the system can also be explained by the formation of boundary waves (2D, as in the case of boundary surface microphones), with an increase in the effect at the edge of circular spaces.
  On and under cupboards, on floors and in front of back walls, even in large halls, small playback systems often appear voluminous (max. 2 x 4 liters, possibly the same polarity). The effect is similar to that of resonance floors, which spread the sound out loud, for example of a tuning fork.
• b) Subjectively, the system appears to have an extended axis far beyond the dimensions of the arrangement and clearly shows a horizontal effect. The vibration axis of the generated waves, which is aligned with the direction of hearing, simulates a very wide, transparent stereo base, in which the heights are surprisingly hardly missed. If the membranes vibrate in opposite directions (same polarity), the stereo base usually narrows in favor of bass reproduction. But even then the effect is very clear with many shots.
• c) It is astonishing that the heights, in relation to the entire room, are usually better audible than in the case of forward-radiating systems. The initially uncompensated frequency response and lack of bass volume have a negative effect. Test persons, including sound engineers, were partly directly in front of the hidden arrangements at a distance of 1 to 4 m, partly in an angular range of up to 90 °. The system was incorrectly located as two dummy boxes in the corners of the room with the same polarity. The listeners moved around space, sometimes in open adjacent rooms, without the effect disappearing. This has never been verified with conventional comparison boxes.

6. The 3D theory

• 6.1 The Gaussian integral theorem
  According to the well-known Gaussian integral theorem, the volume integral delivers the source strength within the volume via a source field and is equal to the envelope integral of the vectors of its flow. The difference between the energy entering and exiting the volume surface corresponds to the energy contained in the volume (cf. Ref. # 1: EA Guillemin, Mathematical Methods of Engineers, R. Oldenbourg Verlag, Munich and Vienna 1966, pp. 237 ff. ). The Stoke theorem describes the current vortex components just as clearly of the field (Lit. # 1, p. 248), as they also occur in acoustics on transducers (microphone, speaker diaphragm).
• 6.2 Theory of a three-dimensional arrangement
  A segment between two spherical shells defines the (conical) shape that a wave radiated concentrically from just one point passes through between two times. In the far field the form degenerates into the cylinder mentioned above. Multiple sources require multiple cylinders or a system of 3 orthogonal components (see hatched segment in Fig. 1a).
  • a) The theory of waves is particularly for compressible media, such as. B. air, complex. Their energy flow also generally consists of vortex fields, such as time-variable rotors or frequencies, and vortex-free, translative fields. In contrast, Gauss's theorem remains vivid: When directional (vectorial) entry of energy (field, wave, particles) into a volume, a difference arises inside the surface of the volume between energy that has already entered and that has not yet emerged. Since these are basic energetic equations, the sentences apply universally to particle fields as well as radiation and wave fields. Each type of energy flow flows through the imaginary side surfaces of a volume. Recording and playback should not falsify this flow of energy, especially reproduce it without reflection. Absorptions and reflections occurring outside of the volume only form mirror sources and characterize the acoustics of the recording room (see Fig. 1a: only radial components).
  • b) Theoretically, such a volume can be chosen arbitrarily. As an equilateral polyhedron, especially as a rectangle or cube, theoretically even one that "breathes" selectively in the direction of each energy flow or sound flow (Polarized) ball that must not breathe concentrically. The cube is the simplest form of everything.
  • c) A cube with an edge length of 50 cm is chosen in the far field. To illustrate this, it does no harm to understand the running energy of the waves as flowing particle streams with certain directions. If the reproduction of the recording should be as true to nature as possible, the recording and reproduction sound transducers must not be separated by bodies (walls, boxes) that change the energy (sound) flow.
• 6.3 A resulting theory on the receiving side
  A passive membrane each, replaced by (several) measuring microphones per side surface, allows the acoustic energy to be measured in and out on the receiving side. Approximately one measurement microphone per surface is sufficient as long as the volume geometry remains small relative to the distance of the (sound) sources from the microphone. The measurement difference between two opposite membranes of the cube describes three vectors in three spatial dimensions, which according to Gauss (see above) describe the current sources in volume approximately. Instead of a one-sided pressure measurement in each direction, there is now a two-sided "flow" measurement, which detects delayed entry and exit energies (differences, vectors). This corresponds to three converter dipoles (see Fig. 1a, 2a with T (L) = natural transit time difference).
• 6.4 The playback page
  In the playback room, an ideally identical (cubic) volume membrane should now reproduce the measurements on the recording side. Each side surface of the above cube can be viewed as a rectangular partial membrane. Ideally, every point on the surface is stimulated so that the inverse effect here the membrane (ring field) generates an oscillation in phase with the receiving space. Theoretically, this would be possible with distributed voice coils per excited membrane. Approximately one converter membrane per surface is sufficient. Ideally, the vibration of the playback cube in the close range acts like that of the recording cube. For each possible direction of hearing, an optimized reproduction of transit time and phase differences now requires two opposite diaphragms of the transducer cube. Two converters per stereo channel would be an optimized dipole. A cross dipole already promises the reproducibility of the horizontal (hearing-adaptive) components).
• 6.5 Theoretical result
  If the playback cube is placed exactly where the recording cube used to be in the recording room after a recording, the original phase correlations (differences) of the recording room should be reproducible far better than previously possible during playback at any location in the playback room . Since the time must be positive, the comparability is probably only valid for one half-space, i.e. those places that lie in the direction of the original sound propagation. But this is the space for the audience anyway.
  • a) The recording and reproducing side volume can theoretically have any shape, so it can also be any polygon (especially cuboid; cone, especially again equilateral) or even a non-concentric "breathing" ball. Even inco-planar arrangements and oblique-angled vector systems are theoretically possible if the runtime differences that occur are sufficiently compensated for or are subjectively irrelevant.
  • b) The cube corresponds to three individual vectorial (polarizing, stereo) arrangements. By means of a stereo dipole according to the invention, the reproduction component that is fictitiously colinear with its vector of the recording space can be generated in each reproduction space. In the near field the energy flow of the recording room is approximately reproduced. A stereo dipole according to the invention, as z. B. is shown in Fig. 2a, covers at most one component (dimension).
  • c) Of all directions, the hearing only needs the one direction in which it is oriented (stereo). Polarized stereophony is therefore only the horizontal component of the locally complete spatial information, which is oriented to adapt to hearing. With only one active membrane, e.g. B. from a planar rectangular speaker of 20 cm as possible, the incoming and outgoing energies in the playback room are reproduced approximately as they were previously measured on the recording side, already simplified by only one microphone per side.
• 6.6 Realization component by component; electronic and mechanical variants
  • a) Two opposite faces of the cube can be considered as a polarized system from a (rectangular) tube and vice versa. Since the mode of operation of each such polarizer according to Gauss is only determined by its behavior on the surface, the internal structure only plays a role in so far as the overall system shows the behavior described to the outside. Even solids can reproduce the behavior of the shell, e.g. B. when electrostatic converters are mounted on the end faces.
  • b) Due to the cancellation of the transverse components of a shaft in the spherical coordinate system (cone, funnel, degenerate to the cylinder coordinate system), the cylinder surface of a dipole should not allow any transverse components. If it is hard, it should have little reflection on the inside. It can also consist entirely of insulating materials as long as the longitudinal (tangential) sound flow does not destroy it becomes. What is important is an energy flow that is reproduced as precisely as possible along each axis or in any direction, in contrast to the obstruction of the energy flow (total reflection, strong curvature) with conventional baffles or through the walls of boxes (i.e. only radial components, as shown in Fig. 1a) ).
  • c) In addition to the polarization, ideal arrangements according to the invention should aim at recording and reproducing analog geometry with the aim of a time-delayed, in-phase membrane oscillation of all microphones and loudspeakers for each stereo channel (depending on the microphone distance). Exact phase correlations improve the fidelity with the runtime-related identical correlation of the phases of the recording and playback in the vicinity of the stereo recording or stereo playback system (see Fig. 1a, 2a with time T (L)).
  • d) Partitions inside always disturb. They hinder the formation of acoustic ring fields according to the invention through the barrier inside, so that with conventional loudspeaker polarity (field in opposite directions) there is no audible effect. With polarity reversal (field in the same direction) or the addition of artificial or system-specific runtimes, however, an audible effect is created, although it is disturbed by reflection. The membrane deflection can even be prevented electronically by reflected (non-signal) components.
  • e) The existence of polarized acoustic fields is often unknown. However, it is known that electromagnetic dipoles by definition cause polarized vibration fields. Mathematically there is also no reason for a separate acoustic wave theory. Then the known basics of other physical dipoles (dipole rows, columns, reflectors) would be transferable. Local (differential) sound pressure and local (differential) sound velocity have analogies in electrical engineering with voltage (E, D field) and current (H, B field).
  • f) The transit time ratios for the sound between the transducers are reproducible in a known manner with transit time elements, which are around 3 ms / m z. B. using "Digital Sound Processor" (DSP) 16-bit shift registers after AD conversion etc. delay. The internal structure of the system is then less relevant.

7. Requirements, electronic system variants

• 7.1 Electronic system simulation
  • a) To achieve the spatial effect, it is sufficient to determine the behavior of an (imaginary) shell of the overall system. B. to simulate electronically. Runtime ratios between the transducers of the arrangement according to the invention are calculated from the distance L between the two transducers of such a system, divided by the speed of sound c = 340 m / s. The delayed signal of the opposite source is superposed on each source's own signal, the high-frequency components of which have been weakened in the mechanical solution. The sum or individual components can also oscillate back and forth several times as a dampened Hall effect. An (almost) undelayed portion resulting from pure reaction behavior (actio = reaction) can be measured and mixed in without any problems. The simple polarity reversal of each component or the loudspeaker corresponds to the respective interposition of a signal inverter (+/-). Such an arrangement is shown schematically in Fig. 1c. The simulation method used here is the subject of claims 23 to 26.
  • b) With variable runtime setting is one for each channel subjective optimum can be determined. Symmetrical running times correspond to the mechanical solution, but can now be varied. Consequently, the teaching according to the invention can also be implemented with circuits with which the behavior of systems according to the invention is simulated in the above-mentioned manner. If the phase (length) of the playback system is also to correlate with that of a recording system, phases that are correlated on the recording and playback side (running times, lengths, distances) should be aimed for (cf. the runtime switching according to Fig. 1d).
• 7.2 Frequency response compensation and measurement according to the new standard
  a) The frequency response of transducers is after installation z. B. in standardized baffles, cars, boxes in the radiation direction of the transducer at 1 watt power measured at a distance of 1 m. This measuring method is unsuitable for measuring the system according to the invention. Because of the lateral radiation, a meaningful measurement can only be carried out close to the so-called "stereophonic main axis" (cf. lecture "2 years spherical microphone", held at the 17th Tonmeister conference in 1992 by J. Wuttke, Schoeps, Karlsruhe). It should also be system-adaptive hearing adaptive, that is, with two lateral transducers, arranged in parallel, e.g. B. by means of an artificial head.
  This new measurement method also implies that system-adequate converters have to be developed for the system which meet these requirements of the system according to the invention for the frequency and phase response. Defects in the frequency response and delay time of the mechanical APS system according to the invention are measured and actively compensated in a known manner, namely electronically. Microprocessors also allow subjectively meaningful modifications.
• 7.3 Parallel radiation of the phases, high base width even with conventional polarity
  Sound transducers with flat membranes are hardly available. More important is the phase accuracy at the poles of the housing. With increasing frequency, conical membranes cause runtime errors up to extinction, which can only be neglected with pipes that are long relative to the transducer diameter. The membrane can also be designed and z. B. be attached in the tube that approximately flat waves still arise. Converters can consequently be shifted inwards, e.g. B. inside a tube. In one embodiment, very phase-accurate converters (JORDAN JX 50, diameter D = 50 mm) are glued into a cylinder rolled up of flexible, permeable foam and having a length of L = 35 cm and sunk into a 40 cm tube with spacers. In spite of low sound pressure, an excellent base width is achieved with the same loudspeaker polarity with such an arrangement, an asymmetry to the axis being negligible. An embodiment of the pipe jacket is illustrated in Fig. 2f and 2g. In Fig. 1c, the pipe is indicated by dashed lines.
• 7.4 Complementary transverse waves superposed
  With the help of subwoofers, missing basses that are irrelevant to location can be added in a previously known manner. In the conventional equipolar operation of the acoustically polarized stereo system (APS) according to the invention, the mono components inflate the tube in the bass region virtually pneumatically and bring about an improved bass reproduction. In addition, a small central opening shows measurable bass reflex effects at half the lower frequency (approx. 50 Hz). The transverse wave can therefore be selectively and superposed for an optimized system of a longitudinal wave. The casing of the new system pumps transversal. This corresponds to the dilation and contraction of the above-mentioned housing cylinder. While the location-relevant frequencies, e.g. B. radiated longitudinally (here via the lateral poles), the radiation of the irrelevant basses can then be purely transversal.
  An electrodynamic dilatation and contraction or quasi "pneumatic" inflation of an elastic second sheath over the above-mentioned fixed tube solve the problem. An expandable cylinder is placed over a lower fixed cylinder, which can "pump" transversely in any frequency in the frequency rhythm (analogy to the illustration in Fig. 1c).

8. From recording to playback, 3D acoustics

• 8.1 Recording systems
  The recording side can also use the equivalent laws, which are only inverse to the speaker system described, for the purpose of polarized, receiver-side reconstruction (each) of an acoustic axis on the recording side. The transfer to the recording side leads to the following theoretical requirements:
  • a) On the recording side, the known pressure gradient microphone (cardioid characteristic) largely corresponds schematically to the construction principle of an acoustically polarizing recording arrangement. The microphone membranes are very close together, in accordance with the meaning of the word "gradient".
  • b) In order to arrive at an arrangement according to this invention, a transmitted gradient of the microphone must now be transmitted separately by channel instead of being summed in one channel. In the sense of a better playback side Correlation with the currently very large transducer geometries, the gradient must also become a noticeable, runtime-defined difference. Therefore, a distance of several centimeters (e.g. 15 to 100 cm) and an undisturbed, but low-resonance inner connection (see above playback system) are required. However, the surfaces of the transducers may theoretically have large membranes in the cylinder coordinate system.
  • c) The acoustic energy flow (vector), which emanates from sound sources on the recording side, would theoretically have to be measured or generated or "flow" through a minimum of two transducers (better: its membranes) instead of with a conventional one-sided pressure transducer for each orthogonal component. An arrangement of a dipole according to Fig. 2a is suitable for the recording.
  • d) The result produced according to the invention with only one playback dipole so far can be improved by a kind of "cross dipole" (see above: Gaussian integral theorem). The invention includes recording systems of the same type, in particular if they are intended for acoustically polarized playback systems according to this invention. A cross dipole can be realized by two polarizing stereo dipoles according to Fig. 1a in a crossed arrangement.
• 8.2 Correlating overall system from recording to playback
  • a) According to the invention, ideally, in the recording and playback room, a phase (membrane movement) of related transducers corresponding to the wave propagation time between the transducers is sought. This is particularly easily achieved in that the same distances between the transducers in the recording and playback room, for. B. 70, 50 or 17 cm (about hearing distance) are observed. Existing differences in the term can for positive time differences by correcting distance-related time constants, e.g. B. be compensated by term elements. Multiple systems (parallel and coaxial, passive and active, delayed) increase the effect. An arrangement for the runtime correction is illustrated in Fig. 1d.
  • b) Polarized vibrations can be transferred to a polarized recording system for each spatial axis. The playback systems can then transmit a polarized image of each coordinate of the recording space. Ideally, the runtime and intensity ratios of the recording space in the reproduction space are reproduced in each axis. This is possible with the same distances between the recording / playback converters.
  • c) The acoustic flow measured component by component via incoming and outgoing energies in the recording room (triggered by loudspeaker membranes) is reproduced in the playback room with the highest possible geometric or runtime-adapted correlation. Theoretically, at least two dipoles with as many as possible four transducers are required for aurally correct reproduction (= a cross dipole with its respective ear-adaptive components). Subjectively, a single stereo dipole is sufficient on the recording and playback side, an antiparallel (180 °) degenerated by superposition and a "cross dipole" that has become monolithic.
  • d) Boxes and baffles arranged with a delay in the playback room are known, but a system itself contains delay differences. The transducers work length-adapted and delayed as far as possible, whereby the sound flow in the room is passed on like a pump. The recording room can be traversed with multiple recording dipole lines (rows, columns) with exact run times. The control of the same phase, channel by phase, except for a time constant (delay) Playback systems in the playback room can then unusually largely reproduce the original sound space. In Fig. 1a the runtime offset is denoted by T.
  • e) The purely subjective, exact electronic compensation of errors in the duration and intensity is difficult. In the system according to the invention, however, two dipole systems are already sufficient to replace four surround speakers of conventional surround systems.

9. Limitations (disclaimer)

• Erzeugte reflektierte Wellen laufen zur Originalwelle invertiert und heben diesen akustischen Fluß z. T. auf.
• Diese stehenden Komponenten verfälschen den Fluß, die originale, primär akustisch polarisierte Charakteristik.
• Der Erfindung entsprechen dagegen Wellen, die bereits invertiert erzeugt werden, um erst durch Reflexion ihre definitive Charakteristik zurückzugewinnen, um weitgehend erst in dieser Form abgestrahlt zu werden.
• Die Physik verlangt gemäß obigen Ausführungen unter 3.2a idealerweise laufzeitadaptiert gleichsinnige Membranauslenkungen. Künstliche Umpolung wirkt spektakulär, korreliert aber selten oder nur mit einer Komponente mit der Aufnahmeseite. Das bedeutet, daß extreme Raumeffekte (Ringfluß) durch Manipulation von Elementen der Erfindung, speziell der Laufzeit, möglich sind, da nur die Wirkung der Systemhülle im Außenbereich des Systems darüber entscheidet.

• 9.1 Konventionelle Mikrofonanordnungen mit gerichteter Wirkung
  Bekannte Aufnahmesysteme mit zwei entgegengesetzt gerichteten Mikrofonen pro Stereo-System haben durchaus manchmal schon einen geringfügigen Polarisierungseffekt, der aufgrund der großen Empfindlichkeit des Gehörs sogar hörbar sein kann. Dies ist aber ein sekundärer Effekt. Dieser Effekt hat ohne explizite, die Wellen primär polarisierende Maßnahmen wie Erzeugung von primär progressiven, also reflexions- und möglichst auch beugungsarmen Wellen entlang Linien einer gehöradaptiven Aufstellung und Aufnahme nach dem o. g. Prinzip mit der Erfindung nichts zu tun.
  • a) Schallwellen im Raum erzeugen auf großen, den Schall gut leitenden Flächen bzw. Körpern zweidimensionale Oberflächen-Wellen (2D-Grenzflächen-Wellen) . Eine solche bereits (von 3D zu 2D) flächenhaft entartete OberflächenWelle wird bekanntermaßen vom Grenzflächen-Mikrofon genutzt, dessen Aufnahmen äußerst räumlich wirken können. Polarisation wird jedoch erst durch eine zusätzlich Krümmung einer bereits flächenhaft entarteten Raumstruktur, z. B. Biegung einer ebenen Grenzfläche zum Rohr oder zur Rohrhalbschale, erreicht. Die Welle entartet in diesem Teilraum zu einer linienhaft (1D) progressiv laufenden, ebenen Welle. Gestreckte Formen, z. B. Zylinderformen, können aufnahme- und wiedergabeseitig solche durch endständige Pole begrenzte Strecken bilden, auch in oder an Grenzflächen.
  • b) Mit dem bekannten Druckgradienten-Mikrofon ist ein erster Schritt in Richtung auf das erfindungsgemäße Mikrofon gemacht. Der schematische Aufbau ist prinzipiell derart wählbar. Gemäß der Erfindung sind aber zwei gleiche Membranen für je einen eigenen Übertragungskanal erforderlich. Außerdem sind die Abstände der endständigen Membranen bei den erfindungsgemäßen Mikrofonen größer gewählt, z. B. entsprechend dem Gehörabstand. Sie nutzen die akustische Polarisation entlang der erzeugten Strecke (Linie).
    Vergleichbares gilt wiedergabeseitig für Druckgradienten-Lautsprecher.
  • c) Eine partiell polarisierte Aufnahme erfolgt z. B. mit dem bekannten ORFT-Mikrofon. Bei diesem verbindet ein Rohr die beiden endständigen Aufnahmekapseln. Die von diesem Rohr weit abgesetzten Kapseln befinden sich schon außerhalb der unmittelbaren Rohr-Richtwirkung und sind zu einem Winkel von ca. 110° geknickt. Da ihr Gesamtabstand nur ca. 17 cm beträgt, ist die Richtwirkung des weit kürzeren Zwischenrohres ohnehin nur gering. Zusätzlich unterscheidet sich dieses Mikrofon hinsichtlich des Innenaufbaus von der erfindungsgemäßen Mikrofonanordnung.
  • d) Das bekannte Kugelflächen-Mikrofon (KFM) weist wie das erfindungsgemäße Mikrofon zwei seitliche, einander gegenüberliegende Wandler auf. Seine Aufnahmen zeichnen sich ähnlich wie bei dem erfindungsgemäßen Mikrofon durch bestechende Räumlichkeit aus. Dieses Mikrofon entspricht jedoch ebensowenig wie der Kunstkopf dem erfindungsgemäßen Vorschlag, weil die Kugel konzentrisch wirkt und jede Polarisation durch Raumachsen (Zylinder- oder elliptische Koordinaten) fehlt.
    • Wiedergabeseitig wäre aber aufgrund viel größerer Wandler ein Kugel-Mittelsegment (besser Ellipse) wählbar.
    • Wie beim Kugelflächen mikrofon (KFM) (seitliche Wandler) ist der Frequenzgang hier bezüglich der Stereo-Hauptachse zu optimieren.
    • Das Kugelflächen mikrofon (KFM) ist auch ein entartetes Grenzflächen-Mikrofon. Letzteres nutzt bereits eine flächig entartete laufende Oberflächenwelle (hier: auf der Kugel umlaufend) aber ohne jede linienhafte Entartung, also Polarisation, gemäß der Erfindung.
  • e) Für Aufnahmen mit Richtmikrofonen werden bekanntermaßen Rohre bei Rohr-Richtmikrofonen und ebene oder Parabol-Reflektoren zur Schallbündelung in Aufnahmerichtung genutzt. Diese Richtmikrofone werden auf eine von mehreren Schallquellen gerichtet, um Nebenquellen auszusondern. Beim Stereo-Dipol wird.primär nicht dieser Richtwirkungseffekt genutzt, sondern hauptsächlich die unselektive, dazu teils orthogonale Charakteristik. Die Gesamtwirkung berücksichtigt unselektiv viele Quellen, besonders die gehöradaptiv gerichtete Charakteristik; sie ist also insgesamt unselektiv. Ein derartiger nicht selektiver Aufnahme-Dipol gemäß der Erfindung, z. B. ein Rohr oder Röhrchen mit eingeklebten Membranen gemäß Abb. 2, möglichst mit Dämpfung, wird dabei höchstens zufällig in Richtung einer bestimmten Aufnahmeschallquelle zeigen, ohne selektiv zu wirken. Wie beim Kugelflächen-Mikrofon zeigen die Wandler nur zufällig auf ein spezielles Aufnahmeobjekt von mehreren.
• 9.2 Wiedergabe-Seite
  Jeder Elementar-Rechteckimpuls einer Schallwelle kann wie ein Druckstoß betrachtet werden, der von einer Luftpumpe erzeugt wird, die auf der zweiten Seite offen oder mit einem zweiten Kolben (Membran) abgeschlossen ist. Bekannte Lautsprecher-anordnungen verwenden aber keine primäre Polarisation im Sinne der Erfindung (weitgehend komplanare, progressive, laufzeitversetzt ebene Welle von meist endständig strahlenden Polen - vgl. Abb. 1a: Radiale Auslenkungen bei T1, T2).
  • Bei idealer Resonanzunterdrückung (speziell Umfangsresonanz) entstehen beim erfindungsgemäßen System weitgehend nur progressive (laufende) Wellen. Sie enthalten dabei keine wesentlichen regressiven oder stehenden Anteile. Die Kombination der erfindungsgemäßen Elemente reproduziert dabei den Effekt mehr oder minder signifikant. Einige sekundäre Resonanz-Anteile toleriert das Prinzip dabei durchaus, speziell im Tieftonbereich.
  • Trenn- und und Reflexionswände lassen den Effekt nur noch partiell (als Sekundäreffekt) wirken. Die entstehenden signifikant reflektierten Anteile und stehenden Wellen (Resonanzen) zerstören dabei weitgehend den primären Polarisationseffekt der monodirektional laufenden Wellen, also die möglichst reine Progression ohne Regression. Durch Überlagerung progressiver und regressiver Wellen entsteht eine stehende Welle, bei Mehrfachreflexion mit einer Frequenzselektion eine Resonanz. Ebenso bilden die Montagewände und andere innere Wände in relevantem Ausmaß Hindernisse für den Energiefluß, der sich dann auf den Außenraum beschränken muß. Die Fehler sind aber aktiv weitgehend kompensierbar.
  • Die Bedingung weitgehend fehlender Reflexion erfüllen aber auch schallschluckende Innenräume (Schallsumpf). Die innere Kopplung zwischen den Wandlern ist zwar gestört, aber das Verhalten der Systemhülle entscheidet. Sie kann durch zusätzliche Maßnahmen, speziell elektronischer Art (selektive Verstärkung, z. B. durch Equalizer, elektronische Kopplungen, simulierte Laufzeiten) zu ähnlichem und gleichartigem Verhalten gebracht werden. Die Laufzeitschaltung T(L) gemäß Abb. 1d korrigiert die innere Kammertrennung.
  • Jede aktive Lautsprechermembran wirkt für die ankommende Welle des anderen aktiven Wandlers (Stereo-Kanals) passiv und näherungsweise wie eine Öffnung. Bei idealer Phasenkorrelation zwischen Aufnahme und Wiedergabe würde der im System aufgebaute transversal wirkende Druck minimal.
  • a) Handelsübliche konische Wandler haben wenig Phasentreue, wodurch die Wiedergabe der Höhen leidet. Relevant schiefwinklig angeordnete Membranen oder Trennflächen sind noch weniger geeignet. Bereits die schiefwinklige Anordnung von zwei im Verhältnis zu wichtigen Wellenlängen großen, ebenen starren Membranen führt durch entgegengesetzte Phasenanteile am selben starren Objekt zu einer Löschung bestimmter Frequenzen. Dazu kommen noch relevante Reflexionen, so daß die Kriterien der Erfindung nicht mehr erfüllbar sind.
  • b) Resonanzen der Gehäuse sind bei den konventionellen Systemen als stehende Wellen (Resonanzverstärker, Baßreflex, Frequenzgang-Glättung) zum Teil erwünscht. Bei dem erfindungsgemäßen System dagegen sollen solche Verfälschungen möglichst vermieden werden. Bei Anordnungen gemäß 2.3 entstehen aber an starren Montage- oder Trennwänden Reflexionen oder Vibrationen, die einen eventuell partiell erzielten Polarisationseffekt mit der superponierten Welle merklich stören. Dafür ist eine möglichst systemadäquate und optimierte Charakteristik der Wandler sinnvoll.
  • c) Die oben unter 2.3c erwähnte "flexible tube" besitzt z. B. eine Trennwand mit harter Schallreflexion. Auch andere Rohranordnungen entsprechen nicht der Erfindung. Dennoch können sie wie am einfachen Rohr bei gleichsinniger oder zueinander (stereophon) systemadäquat laufzeitversetzter Ansteuerung im für den Außenraum relevanten Verhalten ein Ringfeld erzeugen und entsprächen dann dem erfindungsgemäßen System für geringere Qualitätsansprüche.
  • d) In bekannter schräger aktiver oder passiver Anregung von Rohren können grundsätzlich polarisierte (vektorielle) Komponenten erzeugt werden. Eine im Minimalabstand einer starren Schräge früher ankommende Welle stimmt aber nicht mehr mit der später ankommenden, z. B. im Maximalabstand, überein und verfälscht sie stark.
    • Die Schräge verursacht an starren Membranen Laufzeitdifferenzen am selben Objekt, zwischen oben und unten, die bei höheren Frequenzen relevant werden und zur Löschung führen können. Bei flexiblen dünnen Membranen (vgl. MANGER-WANDLER (R)) wird diese Löschung dagegen durch eine auf der passiven Seite quer über die Membran laufende Welle weitgehend verhindert, so daß diese Welle kaum verfälscht in den Außenraum weitergeleitet wird. Beim passiven Durchlaufen eines solchen flexiblen Kontinuums (plastische Haut) bleiben ausreichende Komponenten polarisiert.
  • e) Auch der oben unter 2.3c erwähnte STEREOLITH verursacht Reflexionen, die an den Schrägen teilweise zum Gehäuseboden weitergeleitet und nochmals reflektiert werden. Durch die relativ sehr großflächige schräge Anordnung der reflexionsarmen Lautsprecher sind aber durchaus wesentliche Anteile zwischen je zwei Lautsprechern direkt gekoppelt. Es entstehen für höhere Frequenzen jedoch relevante Phasenfehler, welche durch die unterschiedlichen Laufzeiten der dort verwendeten konischen, starren und zudem noch schräg angeordneten Lautsprecher bedingt sind.
• 9.3 Einige tolerierbare, aber verbesserungsfähige Mängel
  • a) Theoretisch lösen flexible statt starre Membranen einen Teil der Phasenprobleme. Ein komplanares Feldbild ändert sich zudem, infinitesimal gesehen, auch bei leichteren Krümmungen und Knicken nicht relevant. Phasenfehler starrer Membranen in Winkelanordnung wären daher theoretisch weitgehend im Sinne der Erfindung kompensierbar, z. B. durch gebogene Verbindungsrohre im Gehäuseinnern. So könnten durch Modifikationen bekannter Lösungen nach dem erfindungsgemäßen Vorschlag auch axiale Komponenten erzeugt werden.
  • b) Die unangenehme singuläre Umfangsresonanz eines Zylinders sollte möglichst unterdrückt werden, zumal sie meist etwa der gleichen Resonanzfrequenz von eingepaßten, z. B. eingeklebten Wandlern entspricht. Neben einer unökonomischen resonanzhemmenden Wanddicke helfen auch variierende Rohrquerschnitte. Hierbei stellen Ellipsen und Hyperboloide zuverlässige Näherungsformen des Zylinders dar. Querschnittsänderungen erzeugen jedoch bei allen longitudinalen Strömungen bekanntermaßen Querkomponenten. In Querschnittsrichtung aus diesem Grunde verstärkt entstehender Druck und Zug bildet bei allen nichtzylindrischen Formen eine zwangsläufige Störung.
  • c) Der Aufbau von Innendruck-Querkomponenten ist sehr weitgehend durch eine innere Längsstrukturierung, z. B. durch Rohre und Röhrchen eliminierbar. Luftdurchlässig längsstrukturierte, sogar geschachtelte Bündel bewirken eine Dilatation der zunächst kugelförmigen Wellen-Ausbreitung. Die konzentrische Elementarwelle wird in Längsrichtung verformt, z. B. durch längenvariante innere Röhrchen, Wellpappe als effiziente Billigstlösung, aufgerollten Bast und/oder Kunststoffolien mit Abstandhaltern. Eine Ausbreitungsrichtung wird bei diesen Lösungen stärker gefördert, während andere Ausbreitungsrichtungen unterdrückt werden. Ein im Umfang leicht luftdurchlässiges laminiertes Rohr behindert, auch bei einfachen Lösungen, den Druckaufbau und die Umfangsresonanz. Ein Bündel gleich langer Röhrchen kann zur Bildung diverser Grundformen ganz unterschiedlich verformt werden. Verschiedene Querschnittsgestaltungen sind in den Abb. 2e bis 2g und 4 dargestellt und Gegenstand der Ansprüche 7 bis 9.
  • d) Gleichsinnige Ansteuerung des erfindungsgemäßen Systems durch umgepolte Lautsprecher führt bei der Wiedergabe vieler Aufnahmen subjektiv häufig zu einer äußerst spektakulären Öffnung des Raumes. Bei Verwendung von ONE-POINT-Stereoaufnahmen mit großer Korrelation zwischen dem Aufnahme- und Wiedergabeabstand der beiden jeweiligen Schallwandler (48 cm) wirkt die Wiedergabe subjektiv noch breiter und natürlicher.
  • f) Echte Stereosignale besitzen stets Amplituden- und Phasenunterschiede. Diese werden aufnahmeseitig bereits durch gegebene oder bewußte Unsymmetrie bei der Mikrofonaufstellung (z. B. ONE-POINT-Aufnahme) erreicht. Reine Monosignale verursachen bei gleichsinniger Ansteuerung des akustisch polarisierten Stereosystems im schalltoten Raum eine Auslöschung auf der System-Mittelsenkrechten. Auch in Wiedergaberäumen wird diese durch Unsymmetrien und Wandreflexionen korrigiert. Mittels Klangprozessor können Monoanteile auf vorbekannte Art selektiert und, wie bei einem Surround-System, zu einem separat wiedergegebenen Mittenkanal zusammengeführt werden.
  • g) Das erfindungsgemäße System wirkt phasen-stereophon. Wo bisher mehr als zwei Aufnahmekanäle zu einer Art "Mischpult-Stereophonie" zusammengeführt, also summiert und konventionell intensitäts-stereophon (amplituden-stereophon) wiedergegeben worden sind, kann dies Ortungsfehler erzeugen.
• 9.4 Transversal eindimensional polarisiertes Schallfeld
  • a) Aufgrund bisheriger Betrachtungen wird deutlich, daß ein eindimensional transversal polarisiertes Schallfeld durch Bündelung (Schichtung) paralleler Ebenen mit Abstandshaltern statt durch Bündelung von Rohrformen erreicht wird. Wenn z. B. senkrechte parallele Ebenen eine Rohrform bilden, werden die waagrechten Komponenten unterdrückt, da sie zu den Schichten orthogonal liegen, d. h. parallel zu den Flächenvektoren der Schichtung. Anstelle der eindimensionalen, röhrchenförmigen Strukturierung finden zweidimensionale ebene Strukturen (Schichten) Verwendung. Dabei wird nur eine einzige transversale Komponente der Welle unterdrückt. Es ist anzunehmen, daß derart polarisierte akustische Wellenformen auch anders nutzbar sind.
    In Abb. 1b sind Röhrchenstrukturen dargestellt.
  • b) Die oben beschriebene Struktur entspricht der Erfindung. Wird sie z. B. in Längsrichtung eines Rohres aus elastischem Schaumstoff eingesetzt, so wirken z. B. Tieftonkomponenten transversal verstärkt auf den Rohrmantel. Die longitudinal endständigen Mittel- und Hochton-Membranen geben die höheren Frequenzen ab. Um den akustischen Kurzschluß in Wandlernähe zu unterdrücken, kann der Rohrmantel dort steifer als in der Mitte gewählt werden.
  • c) Alle zur jeweiligen Primäranordnung (Wandler, Polarisator) parallelen passiven und aktiven Systeme (interne und externe) können die Polarisation durch Bündelungseffekt verstärken. Allgemein liefern alle parallelen, auch längswärts geschachtelte oder gespiegelte Elemente, eine Effektverstärkung. Parallele Hoch-, Mittel- und Tiefton-Systeme und laufzeitkorrekt phasenversetzte Anordnungen, interne und externe, sind sinnvoll.

Separating or reflecting system walls and kinks block or prevent a progressive flow of energy.

• Generated reflected waves run inverted to the original wave and raise this acoustic flow z. T. on.
• These standing components distort the flow, the original, primarily acoustically polarized characteristic.
• The invention, on the other hand, corresponds to waves which are already generated inverted, only to regain their definitive characteristics only by reflection, in order to be largely emitted in this form.
• According to the explanations above under 3.2a, physics ideally requires diaphragm deflections in the same direction adapted to the running time. Artificial polarity reversal looks spectacular, but rarely or only correlates with one component on the receiving side. This means that extreme spatial effects (ring flow) are possible through manipulation of elements of the invention, especially the runtime, since only the effect of the system shell in the outer area of the system determines this.

• 9.1 Conventional microphone arrangements with directional effect
  Known recording systems with two oppositely directed microphones per stereo system sometimes have a slight polarization effect, which may even be audible due to the high sensitivity of the hearing. But this is a secondary effect. This effect has nothing to do with the invention without explicit measures which primarily polarize the waves, such as the generation of primarily progressive, ie low-reflection and possibly also low-diffraction waves along lines of a hearing-adaptive setup and recording according to the above-mentioned principle.
  • a) Sound waves in space generate two-dimensional surface waves (2D interface waves) on large surfaces or bodies that conduct sound well. Such an already degenerate surface wave (from 3D to 2D) is known to be used by the interface microphone, whose recordings can have an extremely spatial effect. However, polarization is only achieved by an additional curvature of an already degenerate spatial structure, e.g. B. Bending of a flat interface to the pipe or the pipe shell. The wave degenerates into a linear (1D) progressively running, flat wave in this subspace. Stretched shapes, e.g. B. cylindrical shapes, recording and playback side can form such sections delimited by terminal poles, also in or at interfaces.
  • b) The known pressure gradient microphone is a first step towards the microphone according to the invention. In principle, the schematic structure can be selected in this way. According to the invention, however, two identical membranes are required for a separate transmission channel. In addition, the distances between the terminal membranes in the microphones according to the invention are chosen to be larger, e.g. B. according to the hearing distance. They use acoustic polarization along the generated route (line).
    The same applies to the reproduction side for pressure gradient loudspeakers.
  • c) A partially polarized image is taken e.g. B. with the well-known ORFT microphone. A tube connects the two end capsules. The capsules, which are offset far from this tube, are already outside the direct tube directivity and are bent at an angle of approx. 110 °. Since their total distance is only approx. 17 cm, the directivity of the much shorter intermediate tube is only slight anyway. In addition, this microphone differs in terms of the internal structure from the microphone arrangement according to the invention.
  • d) The known spherical surface microphone (KFM), like the microphone according to the invention, has two lateral transducers located opposite one another. Similar to the microphone according to the invention, his recordings are characterized by impressive spatiality. However, this microphone does not correspond to the proposal according to the invention any more than the artificial head because the sphere has a concentric effect and there is no polarization due to spatial axes (cylinder or elliptical coordinates).
    • On the playback side, however, a spherical middle segment (better ellipse) could be selected due to much larger converters.
    • As with the spherical surface microphone (KFM) (side transducer), the frequency response has to be optimized with regard to the stereo main axis.
    • The spherical surface microphone (KFM) is also a degenerate interface microphone. The latter already uses a flat degenerate running surface wave (here: revolving on the ball) but without any linear degeneracy, i.e. polarization, according to the invention.
  • e) For recordings with directional microphones, it is known that tubes are used with directional tube microphones and flat or parabolic reflectors for sound bundling in the recording direction. These directional microphones are aimed at one of several sound sources in order to separate out secondary sources. The stereo dipole does not primarily use this directivity effect, but mainly the unselective, partly orthogonal characteristic. The overall effect takes into account many sources unselectively, especially the characteristics adaptive to hearing; overall, it is therefore unselective. Such a non-selective recording dipole according to the invention, e.g. B. a tube or tube with glued-in membranes according to Fig. 2, if possible with damping, will at most point randomly in the direction of a specific recording sound source without acting selectively. As with the spherical surface microphone, the transducers only point to a special recording object by chance.
• 9.2 Playback page
  Each elementary rectangular pulse of a sound wave can be viewed as a pressure surge generated by an air pump that is open on the second side or closed with a second piston (membrane). Known loudspeaker arrangements, however, do not use primary polarization in the sense of the invention (largely coplanar, progressive, delayed plane wave of mostly terminally radiating poles - see Fig. 1a: Radial deflections in T1, T2).
  • With ideal resonance suppression (especially circumferential resonance), largely only progressive (running) waves occur in the system according to the invention. They contain no significant regressive or standing shares. The combination of the elements according to the invention reproduces the effect more or less significantly. The principle tolerates some secondary resonance components, especially in the low frequency range.
  • Partition and reflection walls let the effect only partially (as a secondary effect). The resulting significantly reflected components and standing waves (resonances) largely destroy the primary polarization effect of the mono-directional waves, i.e. the purest possible progression without regression. By superimposing progressive and regressive waves, a standing wave is created, with multiple reflection with a frequency selection, a resonance. Likewise, the assembly walls and other inner walls form relevant obstacles to the flow of energy, which must then be limited to the outside. However, the errors can be largely compensated for actively.
  • Sound-absorbing interiors (sound sump) also meet the condition of largely no reflection. The internal coupling between the transducers is disturbed, but the behavior of the system shell is decisive. It can be brought to a similar and similar behavior by additional measures, especially of an electronic type (selective amplification, e.g. by equalizers, electronic couplings, simulated transit times). The runtime switching T (L) according to Fig. 1d corrects the internal chamber separation.
  • Each active loudspeaker diaphragm acts passively and approximately like an opening for the incoming wave of the other active transducer (stereo channel). With an ideal phase correlation between recording and playback, the transversely acting pressure built up in the system would be minimal.
  • a) Commercial conical converters have little phase fidelity, whereby the reproduction of the highs suffers. Relevant membranes or partitions arranged at an oblique angle are even less suitable. Even the oblique arrangement of two flat rigid membranes that are large in relation to the important wavelengths leads to the deletion of certain frequencies due to opposite phase components on the same rigid object. In addition there are relevant reflections so that the criteria of the invention can no longer be met.
  • b) In the conventional systems, resonances of the housings are sometimes desired as standing waves (resonance amplifier, bass reflex, frequency response smoothing). In the system according to the invention, however, such falsifications should be avoided as far as possible. In the case of arrangements according to 2.3, however, reflections or vibrations occur on rigid assembly or partition walls, which noticeably disrupt a partially achieved polarization effect with the superposed wave. For this, a system-appropriate and optimized characteristic of the converter is useful.
  • c) The "flexible tube" mentioned above under 2.3c has z. B. a partition with hard sound reflection. Other pipe arrangements also do not correspond to the invention. Nevertheless, they can generate a ring field in the same way as on a simple pipe with actuation that is equivalent to one another or that is (stereophonically) system-appropriately delayed in terms of runtime, and then correspond to the system according to the invention for lower quality requirements.
  • d) In known oblique active or passive excitation of pipes, polarized (vectorial) components can be generated in principle. A wave arriving earlier in the minimum distance of a rigid slope is no longer correct with the later arriving, e.g. B. in the maximum distance, matched and heavily falsified.
    • On rigid membranes, the slope causes transit time differences on the same object, between top and bottom, which become relevant at higher frequencies and can lead to deletion. In the case of flexible thin membranes (see MANGER-WANDLER (R)), on the other hand, this deletion is largely prevented by a wave running across the membrane on the passive side, so that this wave is hardly falsified and passed on to the outside. When passing through such a flexible continuum (plastic skin) passively enough components remain polarized.
  • e) The STEREOLITH mentioned above under 2.3c also causes reflections, which are partly passed on to the bottom of the case and reflected again. Due to the relatively large, oblique arrangement of the low-reflection speakers, however, substantial portions are directly coupled between two speakers. However, relevant phase errors arise for higher frequencies, which are caused by the different runtimes of the conical, rigid and, additionally, diagonally arranged loudspeakers used there.
• 9.3 Some tolerable, but room for improvement
  • a) In theory, flexible instead of rigid membranes solve some of the phase problems. A coplanar field image also does not change, from an infinitesimal point of view, not relevant even with slight curvatures and kinks. Phase errors of rigid membranes in an angular arrangement would therefore theoretically be largely compensated for in the sense of the invention, for. B. by curved connecting pipes inside the housing. Thus, modifications of known solutions according to the proposal according to the invention could also produce axial components.
  • b) The unpleasant singular circumferential resonance of a cylinder should be suppressed as much as possible, especially since it usually fits around the same resonance frequency of fitted, e.g. B. corresponds to glued transducers. In addition to an uneconomical, resonance-resistant wall thickness, varying pipe cross-sections also help. Here, ellipses and hyperboloids represent reliable approximations of the cylinder. However, cross-sectional changes are known to produce transverse components in all longitudinal flows. For this reason, increasing pressure and tension in the cross-sectional direction form an inevitable disturbance in all non-cylindrical shapes.
  • c) The structure of internal pressure transverse components is very largely due to an internal longitudinal structure, for. B. can be eliminated by pipes and tubes. Air-permeable longitudinally structured, even nested bundles cause a dilation of the initially spherical wave propagation. The concentric elementary wave is deformed in the longitudinal direction, for. B. by length-variant inner tubes, corrugated cardboard as an efficient cheap solution, rolled bast and / or plastic films with spacers. One direction of propagation is more strongly promoted with these solutions, while other directions of propagation are suppressed. A slightly air-permeable laminated tube hampers the pressure build-up and the circumferential resonance, even with simple solutions. A bundle of tubes of the same length can be shaped very differently to form various basic shapes. Different cross-sectional designs are shown in Figs. 2e to 2g and 4 and are the subject of claims 7 to 9.
  • d) Controlling the system according to the invention in the same way by means of polarity-reversed loudspeakers often leads subjectively to an extremely spectacular opening of the room when playing many recordings. When using ONE-POINT stereo recordings with a high correlation between the recording and playback distance of the two Sound transducers (48 cm) subjectively appear even wider and more natural.
  • f) Real stereo signals always have differences in amplitude and phase. These are already achieved on the recording side through a given or deliberate asymmetry in the microphone setup (e.g. ONE-POINT recording). Pure mono signals, when the acoustically polarized stereo system is actuated in the same direction in the anechoic room, cause an extinction on the system perpendicular. This is also corrected in reproduction rooms by asymmetries and wall reflections. Using a sound processor, mono components can be selected in a known manner and, as with a surround system, combined to form a separately reproduced center channel.
  • g) The system according to the invention has a phase-stereophonic effect. Where so far more than two recording channels have been merged into a kind of "mixer stereophony", that is to say summed up and reproduced conventionally intensity stereophonically (amplitude stereophonic), this can produce location errors.
• 9.4 Transversely one-dimensionally polarized sound field
  • a) Based on previous considerations, it is clear that a one-dimensionally transversally polarized sound field is achieved by bundling (layering) parallel planes with spacers instead of bundling tube shapes. If e.g. B. vertical parallel planes form a tube shape, the horizontal components are suppressed because they are orthogonal to the layers, ie parallel to the surface vectors of the stratification. Instead of the one-dimensional, tubular structure, two-dimensional flat structures (layers) are used. Only a single transverse component of the wave is suppressed. It can be assumed that such polarized acoustic waveforms can also be used differently.
    Tube structures are shown in Fig. 1b.
  • b) The structure described above corresponds to the invention. Will she z. B. used in the longitudinal direction of a tube made of elastic foam, so act z. B. low-frequency components transversely reinforced on the pipe jacket. The longitudinal terminal mid and high-frequency membranes emit the higher frequencies. In order to suppress the acoustic short-circuit near the transducer, the tube jacket can be selected stiffer there than in the middle.
  • c) All passive and active systems (internal and external) parallel to the respective primary arrangement (converter, polarizer) can intensify the polarization by means of a bundling effect. In general, all parallel, even nested or mirrored elements provide an effect enhancement. Parallel high, medium and low-frequency systems and phase-correct arrangements, internal and external, make sense.

10. Summaries

• 10.1 One-dimensional longitudinal structuring
  A mono source on the tube open on one side creates the polarization effect. The second opening is through a passive membrane, e.g. B. a switched off second speaker, replaceable. Only the stereo arrangements clarify the effect.
  • An actively controlled membrane, e.g. B. a directed pulse, produces the primary progressive sound wave.
  • A second membrane reacting passively with a delay or an opening prevents the build-up of air pressure.
  • The tube bundles the sound longitudinally in the main direction, as is known from the directional tube microphone.
  • The preferably damped interior hardly interferes with longitudinal components; they arrive at the end of the pipe with a delay.
  • An outside shaft running along the pipe is also reproduced with a time delay at the end of the pipe.
  • In contrast to the closed housing, the open tube has no reflective surface in the longitudinal direction.
  • Sensible damping eliminates disturbing, especially peripheral or transverse resonances of the sound wave.
  • This creates a sound flow in a body or around a body that is approximately the same time.
  • Even smaller runtime differences still provide a subjectively recognizable spatial effect.
  • A thin tube that is triggered directly or by the transducer reacts longitudinally at the same time.
  • An opposite membrane can reactively experience a quasi-instantaneous movement in the same direction.
  • Ellipsoids closed by membranes or the center piece of a sphere are approximate forms.
  • Like boxes, tubular housings with finite dimensions prevent the direct "acoustic short circuit".
  • In the bass range irrelevant to location, below approx. 100 Hz, cross-resonances can be permitted.
  • A tube shape is not necessarily cylindrical. Electronic runtime simulations improve the system.
• 10.2 Some essential properties
  • a) The following speaks for sufficient suppression of the existing (transverse) resonances for tangential, i.e. axially directed wave propagation and thus for a, at least locally, clear sound polarization:
    • Tangential drafts can be felt along the (connecting) pipe, especially at bass frequencies.
    • Lateral (axial) sound radiation means that the loudspeakers can hardly be located if the phase is in the same direction.
    • Hearing directed towards the active acoustic dipole works optimally like a receiving dipole.
    • Outer partitions, also positioning behind bodies, can improve the effect. The wave runs around it.
    • Even outdoors, lying on concrete or earth, the system makes the effect clearly recognizable.
    • Longitudinal gaps on top of each other in the laminated cylindrical jacket do not clink even with high control.
    • Even with a corresponding other construction, the housing (tube) hardly vibrates in the transverse direction.
    • The held up to a 2 mm thick stainless steel tube Ear registered z. B. only a quiet, distant sound (in Fig. 4 a laminated tube is shown).
  • b) The patent claims generally characterize methods and apparatus for the primary generation and use of polarized acoustic waves generated by vibrating bodies. The subclaims are directed to specific exemplary embodiments. The selected transducer technology, including unadjusted loudspeakers, transducer pairs not adapted to the polarization principle, currently still non-polarized recording technology, is secondary.
  • 10.3 Some variants
    The polarizers, polarizer shapes, acoustic conductors, effect amplifiers and converters can be used in a variety of ways, e.g. B. can be varied by the following measures:
    • a) By forming acoustically polarized dipoles, specially formed by coaxial arrangement of a pair of transducers with an interposed polarizing material connection, the so-called acoustic conductor for polarization.
    • b) By different main axes of action (polarization axes), in particular geometric longitudinal axes.
    • c) Through bodies (sound conductors, isolators) or their surfaces, with the main direction usable for polarization.
    • d) By approximately circular, elliptical or polygonal, in particular rectangular cross sections.
    • e) By means of rotationally symmetrical acoustic conductors, in particular simple pipes, but also approximately round, elliptical or hyperbolic, double-conical (diamond-shaped) or other angular surfaces of revolution.
    • f) By any cylindrical, especially round, polygonal, z. B. rectangular, sometimes tapered or expanded cross-sections, i.e. varying cross-sectional areas without significant reflection properties.
    • g) By phase-matched excitation, as far as possible, but also intermediate forms up to counter-phase excitation with the aim of stereo playback / recording with a subjectively very spatial, widely broadened stereo base.
    • h) With monodirectionally ordered systems, in particular with several quasi-parallel, also anti-parallel or bundled systems along lines, with the runtime between the systems adapted control.
    • With active systems (amplification of the polarization in space by several systems polarized along lines with assignment of one or more acoustic transducers per polarizer, especially also delayed).
    • With passive bodies, fibers or laminated bodies for longitudinal wave reinforcement (cross wave suppression).
    • With divided polarizers or acoustic conductors, special assignment of one conductor (housing, tube) per acoustic transducer in an opposite, in particular antiparallel arrangement such that the mutual superposition of the individual waves results in a difference or addition wave that has a polarized effect.
    • With parallel or coaxial delayed transducers or complete systems for education of a new system.
  • i) In particular by polarization amplifiers which are effective in a preferred direction (equivalent: transverse suppressors)
    • with directional polarizers made of material bodies, surfaces or bundled (tube) structures,
    • with active and passive polarizers or resonators lying in the excitation axis or (quasi) parallel to it.
  • k) By excitation of longitudinal acoustic waves or polarized surface waves along a polarization line of a body and its use. On the reproduction side, this can even be a direct (electromagnetic) vibration excitation (for example a membrane) on an electrically or magnetically conductive body, especially on or in a metallic tube, so that acoustically polarized vibrations are produced.
    • Transverse polarization resulting from bundled surfaces with distances (parallel planes).
  • 1) By curvature or moderate buckling of the main direction or arrangement axes, especially orthogonal to listeners or on the recording side to natural sources in order to create the best possible spatial impression without direct sound from a loudspeaker, e.g. B. around listeners / sound sources, or directed away from them (to them everywhere approximately orthogonally, i.e. with an axis direction approximately in the direction of the ears).
  • m) By arranging polarized systems in several spatial axes to achieve 2D or 3D effects.
  • n) By means of geometry and / and phase of all membranes and systems coordinated on the reproduction and recording side.
  • o) Systems controlled by auxiliary frequencies (especially high-frequency carrier frequency or resonance), that is, the modulation of any high-frequency, even flat acoustic wave with audible frequencies.
  • p) By replacing an active dipole membrane with a passive, especially the delayed mono playback, whereby two mono sources also receive spatial effects. This can be done by turning off a speaker. Like an opening, the passive membrane prevents the build-up of air pressure inside with the housing vibrating and differs from fixed closures such as partitions or baffles.
  • q) By energetically different acoustic excitation of a polarizing body, especially electrostatic or bipolar excitation of a magnet (instead of using separate loudspeaker membranes, systems can be excited to vibrate axially directly via (two) forces acting on a body or its end faces).
  • r) By any structure or surface (cladding) which is noticeably reinforced in a main direction and which serves for primary polarized reproduction / recording by means of the structure or cladding waves of a body.
  • s) A recording technique of the same kind seems reasonable. In particular, a 2D or 3D system (axis cross of orthogonal polarizers) should convey 3D effects. Rows and columns of such systems are also conceivable - coordinated in terms of runtime during the phase.
  • t) The additional attachment of external separators (insulation material, partition, partition) can be an advantage. This weakens acoustic short circuits in the vicinity of the Arrangement from and thus strengthens the acoustic flow in the far field. Additional attachment of another partition, also between the listener and the arrangement. The arrangement is such that two dipole systems according to the invention replace four boxes of surround systems.
• 10.4 Additional comments
  • a) The overall system forms an active, "acoustically polarized stereo dipole". This is an axial radiator that, like others, e.g. B. electrical, dipoles vibrates and can have two acoustic transducers (speakers, sound sources) at the poles (ends). In the space connected by a preferably damped tube, approximately parallel, polarized equipotential planes form in the connecting axis of this acoustic "conductor": progressively running waves (longitudinal waves, momentum law) form along the surface, ie the jacket. This polarized acoustic dipole should not be confused with previously known dipole speakers.
  • b) On the reproduction side, high frequencies predominantly form flat instead of concentric waves (cf. EP 0 500 294 A2, column 2, lines 11 to 14). However, this otherwise undesirable overly directed structure can now be used in the adaptive (horizontal) direction for location-relevant frequencies. Such horizontally polarized fields, i.e. fields that are co-planar with the ear, should ideally approach a headphone characteristic (180 °), because the wave surfaces hit the ears oriented in the field line direction from left and right, rather than conventionally, from the front. Their direction of vibration is parallel to the auditory axis.
  • c) Each line-like degeneration causes a polarization, which is the aim of the invention to use. As with optical systems and antennas, polarization is known to weaken interfering components of a vibration. This property can also be used in public address systems.
  • d) The gradient of the energy of an (acoustic) source is always a directional quantity, i.e. a vector. Its change over time, the primarily continuous wave (train), is a component that is negatively directed to the incoming wave (pressure). Ideally, this results in a phase-related control of the system. Therefore, recording systems should record all components at a defined distance, possibly also polarized.
  • e) A polarized stereo signal can also be generated with a minimum of two polarized mono sources. Superposition of two ideally antiparallel, separate, polarized mono sources with adaptive hearing leads to a polarized stereo dipole. Both can be integrated in a housing and then coupled. Since an active source in the opposite loudspeaker diaphragm (like an opening) causes a passive diaphragm oscillation, the active signal of this second loudspeaker can be superposed on the first oscillation.
  • f) More than two arbitrarily distributed sources can be z. B. with the three components of their gradients, in an orthogonal axis cross, so form a 3D vector in the direction of the intensity change and the time differences. This completes the spatial information in a way not previously used.

11. From the original idea to the invention

• a) The original idea was that each rod with a fixed length has at least one resonance frequency. The main response is a length that corresponds to half the wavelength. Rods of different lengths from very short to very long should cover the entire audible tower cover and be excited to vibrate in their longitudinal direction. With a loudspeaker attached to the poles of a tube filled with such rods or with a pair of loudspeakers, these rods are excited to vibrate. Instead of rods, glass fibers of different lengths are provided.
• b) On this occasion it was found that the effect found was effective even without these measures, that is, according to the previous description. Apparently it is mainly air-permeable gaps that cause the effect. If you reverse the polarity of a loudspeaker, it can be heard easily and without great effort. Tube bundles of different lengths can be used. At first it was not clear whether the air columns of the tubes of different lengths vibrate and produce the effect. It is surprising that even simple, damped pipes have a clearly recognizable effect in reverse-pole operation, even though the sound pattern is not yet satisfactory, also because of converters which are not system-adequate. With the modifications described, these shortcomings are largely eliminated. The invention reproduces artificially the conditions in the far field of the spherical wave with great subjective gain. This far field shown in Fig. 1a degenerates into the form shown in Fig. 1b.
• c) It still needs to be investigated what proportion the reactive forces have (actio = reactio), which act axially (longitudinally) and with almost no time delay. Due to the extremely high speed of sound in matter, each acoustic conductor could act in a similar way to a HERTZ dipole relative to the resulting (very long) wavelengths in matter, as is known especially from high-frequency technology. You can even assign your virtual mirror source in the interior of the body to each source in the exterior - or vice versa.

Claims (38)

1. Method for reproducing acoustic wave energy having localization-relevant frequency ranges with the aid of at least one sound transducer, characterized in that the wave energy is attenuated or suppressed, or amplified in at least one of the three propagation directions in relation to the other directions by at least one body having selective directivity, which body forms a dipole moment in air with respect to the wavelength of the localization-relevant frequencies used, the propagation direction extending in an aurally compensated manner essentially parallel to the connecting line of a listener's ears.
2. Method for reproducing acoustic wave energy having localization-relevant frequency ranges comprising the following method steps:

   - generation of a sound wave by means of at least two active sound transducers which transmit the relevant frequencies necessary for a localization;

   - polarization of the sound waves by means of at least one body which is coupled directly to the sound transducer and through which the sound waves pass with low reflection essentially along a line of action which is limited by two end faces of the body;
   the vector of the end faces extending approximately parallel to said line of action and a dipole moment, i.e. an acoustic dipole, being formed by the spacing of the end faces of the body;

   - low-reflection transmission of the sound waves exiting from the end faces of said body.
3. Device for performing the method according to Claim 1, comprising at least one sound transducer, characterized in that the sound transducer is connected to a body (AC) which extends in propagation direction P of the sound waves and presents the sound waves with a resistance which is small in the extension direction and is greater transversely to the extension direction so that the gradient has a maximum in the transverse direction.
4. Device for performing the method according to Claim 2, comprising

   - at least two sound transducers which transmit the relevant frequency necessary for localization;

   - at least one body which conducts the sound waves generated by the transducers essentially as a wave travelling along a line of action towards two mutually opposite, easily moved end faces of the body;
   the radiating end faces which limit the body forming an acoustic dipole.
5. Arrangement for stereophonic acoustic reproduction,

   - comprising at least two, preferably directly adjoining devices according to Claim 3 which are aligned essentially in anti-parallel and which are preferably arranged in a single housing.
6. Device or arrangement according to Claim 3, 4 or 5, characterized in that diaphragms of sound transducers are the end faces of the body and oscillate either in the same direction or in opposite directions.
7. Device or arrangement according to one of Claims 3 to 6, characterized in that, in order to prevent resonances, the body (AC) has a sufficient damping of the sound waves in the interior, the damping gradient extending preferably orthogonally to the direction of the line of action.
8. Device or arrangement according to one of Claims 3 to 7, characterized in that the body (AC) comprises a tube extending in the extension direction, a bundle of tubes composed of a plurality of tubes, or bundled, longitudinally laminated, and optionally nested rods or fibres running in the extension direction.
9. Device or arrangement according to one of Claims 3 to 8, characterized in that the body (AC) comprises flat or rolled layers which are closely spaced relative to the wavelength and extend parallel to one another.
10. Device or arrangement according to one of Claims 3 to 9, characterized in that the sound transducer is a loudspeaker (W1, W2).
11. Device or arrangement according to one of Claims 3 to 10, characterized in that the body (AC) has such low reflection in the propagation direction that the flux of the acoustic wave energy propagates essentially progressively in the propagation direction, and regressive components of the wave energy are suppressed.
12. Device or arrangement according to one of Claims 3 to 11, characterized in that each sound transducer has as flat a diaphragm as possible whose area vector is located, in particular, directly on the line of action.
13. Device or arrangement according to one of Claims 3 or 12, characterized in that the body (AC) is a cylindrical tube of metal or plastic, into the ends of which loudspeakers have been inserted, preferably glued.
14. Device or arrangement according to Claim 13, characterized in that the tube has a length of 0.15 m to 1 m, a diameter of 4.5 cm to 10 cm, and a wall thickness of 0.25 mm to 2 mm, and the loudspeakers are wide-band loudspeakers.
15. Device or arrangement according to Claim 13 or 14, characterized in that the tube is composed of metal, preferably of hard-rolled and coiled aluminum sheets.
16. Device or arrangement according to one of Claims 3 to 15, characterized in that the tube is arranged on wall panels which have parallel axes and function as reflectors.
17. Device or arrangement according to Claim 16, characterized in that, for a tube having a length of approximately 1 m, the wall panels have a length of approximately 2.5 m and an axial rotation of between 0° and 70°.
18. Device or arrangement according to one of Claims 3 to 17, characterized in that the tube is arranged in the focal axis of conical section shapes, preferably of hyperbolically shaped areas.
19. Arrangement comprising a plurality of devices according to one of Claims 3 to 18, characterized in that the axes of the dipoles are aligned parallel to one another.
20. Arrangement according to Claim 19, characterized in that a plurality of bodies (AC) which are provided with sound transducers are bundled and arranged in such a way that their axes extend in parallel, in particular coaxially and/or in nested fashion, the sound transducers, in particular, being driven by signals having identical or offset propagation times.
21. Arrangement of a plurality of devices according to one of Claims 3 to 18, characterized in that the axes of the dipoles are aligned in a plurality of spatial axes which are preferably orthogonal to one another.
22. Arrangement according to one of Claims 16 to 21, comprising a plurality of sound transducers, characterized in that the acoustic reproduction range is divided into several frequency ranges, at least one sound transducer being provided for each of the frequency ranges of the reproduction range and an acoustic dipole being formed for at least one frequency range.
23. Method according to Claim 2, characterized in that the sound transducers are actuated for the stereophonic reproduction by utilizing natural or artificial propagation times, and the sound wave oscillations generated by them are superposed with a time delay, either wholly or partly, on the oscillations of the respective other sound transducer.
24. Method according to Claim 23, comprising at least two sound transducer systems, each of which is associated with one channel respectively, characterized in that the signals of one channel are superposed on components of the signals of the other channel, which are offset in time, in order to simulate electronically natural propagation-time or frequency conditions.
25. Method according to Claim 23 or 24, characterized in that the frequency and/or phase response is preferably linearized by means of active electronic compensation circuits.
26. Method according to Claim 23 or 24, characterized in that the phase can be varied for subjective optimization, preferably by means of variable propagation times.
27. Method for recording acoustic wave energy having localization-relevant frequency ranges with the aid of at least one sound transducer, characterized in that the wave energy is attenuated or suppressed, or amplified in at least one of the three propagation directions in relation to the other directions by at least one body having selective directivity, which body forms a dipole moment in air with respect to the wavelength, the propagation direction extending in an aurally compensated manner essentially parallel to the connecting line of a listener's ears.
28. Method for the stereophonic recording of acoustic wave energy comprising the following method steps:

    - generation of a sound wave by means of at least two sound transducers;

    - polarization of the sound wave by means of a body which is coupled directly to the sound transducers, and through the interior of which body the sound waves pass with low reflection essentially along a line of action which is limited by two end faces of the body;
    the vector of the end faces extending approximately parallel to said line of action and a passive acoustic dipole being formed by the spacing of the end faces of the body;

    - low-reflection entrance of the sound waves into the end faces of said body.
29. Device for performing the method according to Claim 28, comprising

    - at least two sound transducers;

    - at least one body which conducts the sound wave generated in the transducer essentially as a wave travelling along a line of action between two opposite, easily moved end faces of the body,
    the faces which limit the body forming an acoustic dipole which can be aligned in an aurally compensated manner relative to the line of action of the receiver, in particular the connecting line of a listener's ears, preferably parallel to it.
30. Arrangement for stereophonic recording,

    - consisting of at least two, preferably directly adjoining devices according to Claim 29, which are aligned essentially in anti-parallel, and which are preferably arranged in a single housing.
31. Device or arrangement according to Claim 29 or 30, characterized in that the diaphragms of the sound transducers are the end faces of the body.
32. Device or arrangement according to one of Claims 29 to 31, characterized in that, in order to prevent resonances, the body sufficiently dampens sound waves in the interior, the damping gradient extending preferably orthogonally to the direction of the line of action.
33. Device or arrangement according to one of Claims 29 to 32, characterized in that the body contains longitudinally laminated fibre or tube structures which extend, in particular, along its lines of action.
34. Device or arrangement according to one of Claims 29 to 33, characterized in that each sound transducer has as flat a diaphragm as possible.
35. Arrangement comprising a plurality of devices according to one of Claims 29 to 34, characterized in that the axes of the dipoles are aligned parallel to one another.
36. Arrangement comprising a plurality of devices according to one of Claims 29 to 34, characterized in that the axes of the dipoles are aligned in a plurality of spatial axes which are preferably orthogonal to one another.
37. Arrangement according to one of Claims 35 or 36, comprising a plurality of sound transducers characterized in that the acoustic recording range is divided into a plurality of frequency ranges, at least one sound transducer being provided for each of the frequency ranges of the recording range and an acoustic dipole being formed for at least one frequency range.
38. Device or arrangement according to one of Claims 3 to 22, characterized in that it corresponds to the recording device or arrangement according to Claims 29 to 37 in respect to its geometry and/or phase of the transducer diaphragms.

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